Photosensitive elements suitable for use in printing plates and information recording films are well known and are the subject of a great many publications and patents. Due to the increasing cost of silver, efforts have been made to displace silver halide as the photosensitive material in photosensitive elements with more or less success. Many of these non-silver containing photosensitive elements have utilized compositions containing moieties which polymerize on exposure to suitable radiation to yield a polymer in exposed areas of the element.
In recent years photosensitive elements using photolabile blocked surfactants have been developed. Such surfactants are compounds characterized by a hydrophobic group and at least one polar hydrophilic group, the polar group(s) being masked by a covalently bonded labile masking group. Because of the photolabile mask, the masked surfactant has substantially reduced surfactant activity as compared to the same surfactant in the unmasked state and, on exposure to suitable radiation, the mask is removed, substantially restoring the surfactant to its original surface activity.
U.S. Pat. No. 4,369,244 and copending patent application U.S. Ser. No. 177,288, filed Aug. 11, 1980, U.S. Pat. No. 4,478,967 disclose photosensitive imaging materials and a peel-apart imaging system based upon surfactant compounds whose surfactant activity is blocked by masking groups which are photolabile. On response to suitable radiation the surfactant is released and causes a change in adhesion of the layer in which it is situated relative to an adjacent layer (normally an opaque frangible layer). Peel-apart development can give a visible image. The radiation which may be used is determined by the absorption of the masking group and this may be modified to some extent by substituents on those groups. Thus the o-nitrobenzyl group absorbs at about 250 nm whereas the dimethoxy benzyl group absorbs at about 350 nm. The latter however is a less stable masking group than the former. Such photolabile masked systems are limited in their spectral sensitivity to the ultra violet or extreme blue regions of the spectrum. Attempts to modify the benzyl masking groups in U.S. Pat. No. 4,369,244 to give longer wavelength sensitivity by substituting the benzene ring with, for example, methoxy groups as in Formula I ##STR1## have resulted in much lower stability (i.e., poor shelf life) of the photolabile groups.
Masking (protecting) groups which are photolabile are discussed in detail in Amit et al., "Photosensitive Protecting Groups", Israel J. of Chem. 12 (1-2) 103 (1974) and V.N.R. Pillai, "Photoremovable Protecting Groups in Organic Synthesis", Synthesis, 1-26, January 1980. All the groups discussed are activated by radiation in the wavelength range of 200-400 nm. Although choice of the substituents on the groups determines the absorption peak in this range no mention is made of separate spectral sensitizing compounds being used.
Spectral sensitization of silver-containing photographic materials may be accomplished by incorporating certain organic dyes (sensitizer compounds) in the photosensitive layer. U.S. Pat. Nos. 3,729,313; 3,741,769; 3,808,006; 4,069,054; and 4,250,053 disclose photopolymerized or photoinitiated systems which are sensitized to radiation of longer wavelength than near UV by the addition of sensitizer compounds.
U.S. Pat. No. 4,343,893 discloses masked photographic developer compounds where the developer moiety is released by electron transfer from an alkali to the masking moiety without the absorption of radiation.